This invention relates to a magnetic core material made of Fe-Co base alloy for use at high frequencies, and which has excellent high-frequency alternating magnetic properties. The core material is used in a head core and a plunger yoke of a dot impact printer, and further in a stator and a rotor of a pulse motor.
Such a magnetic core material for use at high frequencies with high frequency signals usually should have a characteristic that a magnetic flux induced due to an applied current rises, and eddy current losses due to an excess current are reduced by making a current resistance ratio of the magnetic core large. Therefore, most magnetic core materials are made of an Fe base casting alloy and have a relatively large current resistance ratio, and excellent magnetic properties. The materials have a composition of 2-3.5% by weight Si and the remainder of Fe and unavoidable impurities. Throughout the following, all percentages refer to weight percentages.
Recently, a word processor, for example, needs to be small-sized and to have high-performance. Therefore, a material of high saturated magnetic flux density should be utilized for a head core of a dot impact printer in order to form a compact head core. In order to meet these requirements, attempts were made to use an alloy of high magnetic flux density, e.g. 50% Fe-50% Co casting alloy, instead of said Fe-Si casting alloy mentioned above (See "Preliminary Lecture Paper of the 23rd autumn Meeting", Japan Electric Material Technique Association). However, such an alloy of high magnetic flux density has lower high-frequency magnetic properties than one expects, partly because of a small current resistance. A magnetic core material made of said Fe-Co alloy has a poor magnetic flux rise because of a large eddy current loss. Therefore, the magnetic core material made of the Fe-Co alloy cannot meet the requirements of high-speed printing operations and clarity of printing which are needed in a word processor.